I am having issues with outgoing e-mails

I am having issues with outgoing e-mails

Hi,
I am unable to send messages both trough my own Applemail and through Zoho mail, Reason 553 relaying disallowed. Invalid Domain

This may be caused by a previous domain expiry ...

I also get notifications that my MX configuration and DKIM entries are not configured even though I since yesterday have tried to set it up according to guidelines in my Shopify domain settings.

Hope you can assist me in these issues.

Kind regards,
Marianne